Regeneration of a particle filter sometimes occurs naturally when the temperature of the exhaust gases has reached the level required to burn the particles present in this filter.
However, under certain engine running conditions, the exhaust gas temperature is not sufficient to provide regeneration of the filter and it is then necessary to artificially initiate combustion of the particles when fouling of the filter has reached a certain threshold.
It can consist in increasing the temperature of the filter above 550° C., generally by temporarily raising the air/fuel ratio of the exhaust gases flowing therethrough without a ratio 1 being reached, and in obtaining an oxidizing composition of these gases to achieve combustion of the particles retained in this filter.
This involves the major drawback of increasing the fuel consumption.
Another technique consists, as described more in detail in European patent EP-0,341,832, in arranging a catalyst for oxidizing the nitrogen monoxide (NO) upstream from the filter. This catalyst oxidizes the nitrogen monoxide contained in the exhaust gases to nitrogen dioxide (NO2) and this nitrogen dioxide is then used to allow combustion of the particles trapped on the filter at a temperature ranging between 280° C. and 400° C.
This technique requires a diesel fuel with a very low sulfur content (of the order of 50 ppm) to maintain a sufficient conversion efficiency of the oxidation catalyst so as to obtain a large amount of NO converted to NO2.
Other techniques involve a chemical process wherein organometallic additives, such as cerium for example, are added to the diesel fuel so as to obtain combustion of the particles present in the filter at a temperature close to 400° C. to 450° C.
Using such additives is quite costly and requires a particular device for feeding these additives notably into a diesel fuel tank.
It is also well known to heat these exhaust gases by means of additional devices arranged in the exhaust line and upstream from the filter, such as burners or resistors, as described more in detail in patents FR-2,753,393 and FR-2,755,623 filed by the applicant.
In this configuration, it is necessary to provide a high amount of heat energy to the exhaust gases, either by burning a large amount of fuel when using a burner, or by using a high electric power in the case of resistors.
The major drawback thereof is that it significantly increases the fuel consumption of the engine and decreases the driving comfort.
The present invention aims to overcome the aforementioned drawbacks by means of a method and of a device allowing to reach regeneration temperatures very rapidly while minimizing consumption.